Monoethylene glycol is used as a raw material in the manufacture of polyester fibres, polyethylene terephthalate (PET) plastics and resins. It is also incorporated into automobile antifreeze liquids.
Monoethylene glycol may be prepared in a highly selective process from ethylene oxide via ethylene carbonate. This is typically carried out in a two-step process wherein the first step is the reaction of ethylene oxide with carbon dioxide to form ethylene carbonate, and the second step is the hydrolysis of ethylene carbonate to form ethylene glycol.
In U.S. Pat. No. 6,080,897, ethylene oxide reacts with carbon dioxide to form ethylene carbonate in a carboxylation reaction apparatus consisting of a first bubble column, a second bubble column and a gas-liquid separator. The liquid phase from the separator is passed to a tubular reactor, and the reaction solution from the tubular reactor is passed to a hydrolysis apparatus composed of a first vessel and a second vessel connected in series. The carbon dioxide released in the hydrolysis reaction is compressed and recycled to the carboxylation reaction apparatus.
In JP 11-269110, ethylene oxide reacts with carbon dioxide and water in the presence of a catalyst to form ethylene carbonate and monoethylene glycol in a loop type reactor with an ejector. A part of the reaction solution is extracted from the lower portion of the reactor and the extracted portion is circulated using a pump and injected into the upper portion of the reactor via an ejector nozzle. Heat from the exothermic carboxylation reaction is removed by cooling the extracted reaction mixture in a heat exchanger. In the example, the reaction mixture from the reactor contained 61.1% monoethylene glycol and 37.1% ethylene carbonate. Subsequent hydrolysis and distillation provided high quality monoethylene glycol. A similar system is disclosed in JP 2001 233831.
The present inventors have sought to further improve the manufacture of alkylene glycol from alkylene oxide.